1. Field of the Invention
The present invention relates to an exposure apparatus and a method of manufacturing a device using the same.
2. Description of the Related Art
An exposure apparatus is employed to manufacture micropatterned semiconductor devices such as a semiconductor memory and a logic circuit using photolithography. The exposure apparatus projects the pattern of an original onto a substrate by a projection optical system to expose the substrate. A pulsed emission laser (pulsed light source) such as a KrF, ArF, or F2 excimer laser, for example, can be used as a light source for exposure. Also, a reticle stage and a wafer stage have their positions measured by position measurement devices such as laser interferometers, and are driven by stage driving mechanisms based on the position measurement results.
In substrate exposure, an original and a substrate must be precisely aligned with each other. To do this, it is necessary to detect the positional relationship between an original stage which holds the original and a substrate stage which holds the substrate. By additionally detecting the positional relationships between the original and the original stage and between the substrate and the substrate stage, the positional relationship between the original and the substrate can be detected. Based on this detection result, the original and the substrate can be aligned with each other.
A known scheme of detecting the positional relationship between an original stage and a substrate stage is as follows. First marks are arranged on the original stage, and second marks and a photoelectric conversion device which detects light having passed through the second marks are arranged on the substrate stage. The substrate stage is moved while causing light supplied from a light source to enter the photoelectric conversion device via the first marks, a projection optical system, and the second marks. When a signal output from the photoelectric conversion device has a maximum level, the substrate stage is at a position where the first marks and the second marks have an optimum positional relationship. Note that when a signal output from the photoelectric conversion device has a maximum level upon moving the substrate stage within a plane perpendicular to the optical axis of the projection optical system, the substrate stage is at a best alignment position. When a signal output from the photoelectric conversion device has a maximum level upon moving the substrate stage along the optical axis of the projection optical system, the substrate stage is at a best focus position.